Titanium base alloy and method of processing same



Oct. 21, 1958 M. B. VORDAHL 2,857,259

TITANIUM BASE ALLOY AND METHOD OF PROCESSING SAME Filed July 11, 1957 3 INVENTOR.

MLTONB VEDEDAHL.

MM M m A TTORNEYS atent ()fiice Patented Oct. 21, ease Application July 11, 1957 Serial No..67 1,316 32 Claims. -(Cl. 75-1755) This invention v.pertainsto strong and ductile wrought titanium base alloys, characterized by a microstructure consisting of a coherent admixture of small bodies of alpha titanium and beta titanium, and to methods of producing same, and to Wrought articles thereof.

The. invention (pertains more particularly to wrought titanium .base allows of the character aforesaid, containing about 2 .to 15 atomic percent in aggregate, of one or more .beta .promoting elements such as manganese, chromium, molybdenum and iron. The wrought binary alloys of the vinvention will thus, of course, contain about .2 to 1.5 atomic percent of either manganese, chromium molybdenum .or iron. The corresponding weight .percents are approximately 216% each for iron .and manganese, about 243% for chromium, and about 425% ffor molybdenum. For the ternary and higher order alloys, the aggregate content of these elements shall be, as .above .stated, about "2 to 1'5 atomic precent, with -lowereifective limits for the individual elements of about 0.5% byweight each for molybdenum, manganese, iron and chromium. The alloys :of the invention are strengthened Without undue embrittlement by additions .of up .to about 0.5% carbon and up to about 0.31% of oxygen, .and up to about'0.1'.'% nitrogen.

.These :alloys may be produced by are melting in a .cold-mold furnace,in an inert atmosphere such as argon,

or by equivalent procedures. The titanium employed may be either the high :purity iodide titanium or the commerical purity product obtained by the magnesium reduction of titanium tetrachloride, or an equally pure material as obtained by other procedures.

The invention Will now be described in its various aspects .morein detail with reference to the accompanyingdrawings wherein:

Fig. l isa photomicrograph of a titanium-manganese alloy in laccordance with the invention, containing about 4.1% manganese, balance titanium of commercial purity, the photomicrograph having been taken after subjecting the alloy to 90% reduction in the two-phase or mixedalpha/ beta field.

Fig. 2 is a photomicrograph of a similar binary alloy containing about 6.8% manganese, balance titanium of commercial purity, this alloy having been extensively worked or plastically deformed at a temperature Within the two-phase field, thereupon quenched from a temperature of about700' C., andstabilizedat about 500 C.

Fig. 3 is a partly theoretical phase diagram of the titanium-rich end of the binary titanium-manganese system.

The low temperature or alpha phase of substantially pure titanium, which is of close-packed hexagonal structure, transforms at a temperature of about 885 C., to the high temperature or beta phase, which is of bodycentered cubic structure. The presence of such alphapromoting alloying elements as carbon, oxygen, nitrogen and aluminum "tends to raise the beta transformation temperature, and establish a relatively narrow zone or field of mixed alpha-beta structure. The presence'of'betapromoting alloying metals, prominent among which are at progressively lower temperatures, and establish -a mixed alpha-beta field of substantial scope. Other betajpromoting elements, such as vanadium, columbium, and tantalum have a similar efiect. A typical phase diagram for an alloy of this type is shown in Fig. 3, the system selected for the purpose of illustration being the titanium-manganese system. The-dotted line represent probable boundaries which 'have not been exactly determined.

The present invention comprises, in-one of its aspects, the discovery of a method for imparting to titanium base alloys of the type aforesaid an interleaved dispersion or distribution of the alpha and beta phases, and of a unique microstructure resulting therefrom. An essential step in the method is the plastic deformation of thealloy at a temperature within the two-phase or mixed alphabeta -field. Another essential step is the selection of a titanium base alloy composition possessing two or more ductile phases stable over a suitable temperature range. Such plastic deformation of such a structure dilfers widely from the generally accepted practice of deforming to a desired size and configuration in a "single phase field, and subsequently heat treating to secure a desired set of properties. In the practice of applicants method, the essentials of the 'desired structure are established by plastic deformation, and While subsequent heat treatment is permissible and may -be further beneficial, it must be so controlled as not to destroy the essential structure set up by plastic deformation.

The alloys amenable to the present invention are of the mixed-phase structure typified by the alpha-plusbeta field of the phase diagram, Fig. 3. They are characterized by the presence of two phases of unequal strength, both of which possess some ductility but which deform by basically difierent crystallographic mechanisms. Thus, a stress concentration in one phase tends to diffuse, rather thanto propagate, when it encounters the other phase. The titanium base alloys particularly disclosed by this specification possess all of the unusual .set of qualifications: their alpha phase is relatively weak but quite ductile; their beta phase is relatively strong While nevertheless maintaining some ductility; and alpha, being a hexagonal close-packed structure, deforms in a basically different manner than does beta, which has a body-centered cubic structure.

The present invention is particularly directed to sheet, wire and rod products in which service stresses are applied substantially parallel to the rolling or drawing direction and in which, therefore, the optimum distribution of the weaker phase is in thin fibrils or platelets Whose longitudinal axes are parallel to the rolling or drawing direction. The presence of the Weaker phase in thin fibrils or platelets disposed parallel to the Working direction, presents a minimum area of weaker phase normal to the applied stress and so constitutes thestrongest distribution. Conventional processing procedures such as working in the all-beta region followed by cooling at any convenient rate produce a distribution of the weaker phase which presents an appreciably greater area of weaker phase normal to the applied stress than that achieved by the novel processing disclosed in this invention and so is weaker. A further important advantage of the optimum distribution is that a stress concentration arising in the stronger phase (which is making phase should predominate in order to give higher strength and thus tends to be continuous in the worked and, therefore, the load-bearing direction. Even if it is not continuous, however, its fibrils and platelets are coherent with their contiguous material and so, like the fibrils in a textile thread, act as if they were continuous. It is an essential feature of this invention that, normal to the direction of working, neither phase is continuous.

The history of the alloy prior to plastic deformation in the two-phase field is of little, if any, significance. The effect of plastic deformation in the two-phase field is to increase ductility at a given strength level, and this effect is quite independent of prior history. Whether the specimen has been hardened by quenching from a beta field or lower temperature, or has been fully annealed by slow cooling from a beta field temperature, or given any other treatment, extensive working in the two-phase field still develops its optimum properties, viz., the highest ductility at a given strength level. For example, the quenching from the all-beta field of a binary alloy of 4% manganese, balance substantially all commercial purity titanium, results in a structure characterized by extended martensite-like plates of alpha and irregular bodies of retained beta. The quenching from the allbeta field of a similar alloy containing about 7% manganese produces unstable beta grains. On subsequent elevated temperature aging or service there is a tendency to the growth of continuous bodies of alpha at the grain boundaries. Both structures are predisposed to fracture along the extended region of relatively weak alpha. If either alloy is slow cooled it becomes dead soft and is, for most uses, in its least serviceable condition. Extensive two-phase working of either of these alloys from either the quenched or the annealed condition develops properties identical with those developed by working the same alloy from the other condition.

Extensive plastic deformation such as can be obtained in rolling sheet or rod or in drawing wire at a temperature 7 within the two-phase field has the effect not only of breaking up and dispersing the continuous masses, particularly the relatively weak alpha, and reducing such continuous masses to much smaller, substantially discontinuous and discrete particles, but also of producing the interleaved structure of fibrils and platelets of alpha and beta which is disclosed by this specification as being optimum. If one phase predominates, it tends to form a matrix in which island platelets or fibrils of the second phase are embedded.

Fig. l is a photomicrograph at 600 magnification of a longitudinal section of a sheet of an alloy of commercial purity titanium with 4.1% manganese after a 90% area reduction by rolling at a temperature of 650 C., and stabilization for one hour at a temperature of 550 C. The lighter colored constituent is alpha titanium; the darker one is partially transformed beta. The dispersion and discontinuity of the phases, particularly the alpha phase, are very clear and are substantially optimum for sheet, a good balance being struck between properties transverse and parallel to the working direction. The platelets, which in the longitudinal section of Fig. l are shown edgewise, are arranged parallel to the sheet surfaces. In a wire, the fibrils would be arranged parallel to the axis, and the structure is comparable with that of a cable as compared with a solid rod. The individual fibers of the stronger but more brittle phase can, to some extent, yield separately and thus distribute the load throughout the whole, while the efiect of stressraising voids, lattice imperfections, and the like, tends to be nullified at the first junction with the weaker and more ductile phase.

A typical specimen of the 4.1% manganese alloy in the condition illustrated in Fig.1 has a yield strength in excess of 120,000 p. s. i., an ultimate strength above 145,000 p. s. i., an elongation in /2" .of 16%, and a 4 bend ductility of 3.3 T. This ratio of ductility-to strength is definitely superior to any obtainable from this alloy without extensive plastic deformation at a temperature within the two-phase field. The same is true of the numerous other alloys which have been found amenable to the processing of this invention. An alloy of 7% manganese, balance substantially all commercial purity titanium, after 75% area reduction by rolling at a temperature of 650 C., shows a structure substantially similar to that of the 4.1% manganese alloy illustrated in Fig. 1. Prior to such warm working and after furnace cooling from 750 C., it showed a heterogeneous mass of variously oriented extended bodies of the two phases. After 75 warm rolling and stabilization for one hour at 550 C., alloys of commercial titanium with about 8% manganese show a yield strength of about 145,000 p. s. i., an ultimate strength over 157,000 p. s. i., an elongation in /2 of about 16%, and an average bend ductility of about 3 T.

While the broad invention contemplates plastic deformation at any temperature within the two-phase field at which the strength of the alloy permits such deformation, the Working temperature should not too closely approach the boundary temperature between the mixed alpha-beta field and the beta field. The heating of the alloy prior to working and possibly local heating induced by working itself promote transformations toward equilibrium at the particular temperature. If the working temperature is too close to the all-beta temperature, the tendency to beta formation is so great that a substantial part of the benefits of the invention may be lost. In general, the working temperature should not approach the all-beta temperature within about 50 to C. The preferred temperature range for plastic deformation is from about 400 C. to about 50-100 C. below the beta transus temperature.

The beta transus temperature for any particular alloy in accordance with the invention may be determined by quenching specimens from progressively higher temperatures, until a completely martensitic or retained beta microstructure is obtained.

Increasing amounts of plastic deformation within the two-phase field effect increasingly complete dispersion and interleaving of the phases, and proportionately increase ductility at a given strength level. Generally stated, strength is a function of composition and conditions of stabilization subsequent to two-phase temperature working. For an alloy of given composition, it has been found possible, by appropriate stabilization, to maintain a substantially constant strength-level throughout varying amounts of plastic deformation. Any material variations in strength being thus eliminated, the progressive increase in ductility with increasing two-phase temperature deformation has been established, without complication by other variables. The experimental work leading to the present invention was exhaustive, comprising different alloys, different treatments prior to twophase working, dilferent working temperatures, and varying amounts of two-phase temperature deformation.

As an example of the work, the following series of tests is described. Three alloys were selected which contained, respectively, 3.5%, 4.1% and 4.7% manganese, balance substantially all commercial purity titanium. An ingot of each composition was forged at 870 C. to a /2" to /8" slab, each slab was cleaned and rolled to about 815 C., to sheets of four different thicknesses so chosen that the varying amounts of warm rolling reduction (to be described) resulted in specimens of the same thickness, i. e., all finished specimens received the same total reduction from the ingot. Each of the The measurement of bend ductility is not standardized. The present applicant and his associates measure this property as the radius over which the specimen can be bent to an angle of 75 without cracking, the radius being expressed as a multiple of specimen thickness.

ages-mes tweive sheets snban'wieeaintg tarts, and the three parts r spect y or ea'ch sheet 'were eonditjioii'ed for two-phase temperaturejrolling by three different treatments, "fol-lows:

Condition Q-Heated in air one hour at 815 0, water quenched;

Condition QT-I -Ieated in air onehour at 815 C.,

water quenched, and tempered sixteenhours at 550 Condition F- -Heated in air one hour at 815 C furnace cooled.

" Bend Pre-Rolling Percent Yield Ultimate Percent- 'Duetility Condition Reduc- (1;o00s (1,000s' Elonga- {(Least 'tion p.'s. 1:) p.'s.'i.) trim Favorable Direction) Composition: 4.7% manganese--balance commercial titanium.

Rolling temperature: 700 C.

Stabilized 1 hour at 550 C. after rolling.

I Bend Pre-Rolling Percent Yield Ultimate Percent Ductllity Condition Reduc- (1,000's (1,000s Elonga- "(Least tion p. s. i.) p. s. 1.) tion Favorable Direction) 30 119 137 8 1O 60 128 141 6 10 75 121 136 17 6. 4 90 112 132 19 3. 1 30 124 138 10 60 124 137 6 I 6. 2 75 121 136 9 l 3. 4 90 111 132 21 1 2. 3 30 110 134 6 6.6 60 115 138 13 i 6. 6 75 111 135 16 3. 1 90 113 135 17 2. 3

Composition: 4.1% manganese-balance commercial titanium.

Rolling temperature: 565 C.

Stab1l1zed 1 hour at 550 C. after rolling.

1 Bend Pre-Rolllng Percent Yield Ultimate Percent Duotility Condition Reduc- (1,000s (1,000s Elonga- (Ii'east tlon p. s. i.) p. s. 1.) tion Favorable Direction) E30 117- 140 3 1o 60- ,1301 144 13 10 75 128 141 '7 ,7. 6 90. 125 139 *12 6.2 0 1:10- .136 ,71- 10 60 114 135 12 7.8 75 119 134 14 "6.4 90 123 .134 .18- a. s 30 107. 132. 6 10 60. 5111.": 134 121 6. 4 .75 109 132 44 4. 6 90 1'13 "132 18 '3. 9

about 8% "being about 23% and 43 In the foregoing tables, each of the reported values is the ayer'ag'e of four different tests. The temperature oi? 815 -'C. to which all of-the alloys were heated p ior to the two-phase rolling, if not within the all-beta field lies so close to the all-beta field as to destroy the eifect of previous working. The tabulated results definitely snow for each alloy rolled from each of the three prerolling conditions, first, a negligible variation in yield and ultimate strength with varying amounts of two-phase temperature rolling; and, second, a progressive increase inductility for increasing amounts of such rolling. These effects are "the same fat any of the three rolling tempera- .tures. Other variables being eliminated, increasing amounts of plastic deformation in the two-phase field eifect a progressive increase in ductility.

Stabilization, as above described, is desirable under most conditions, and can -be performed at temperatures up to about 550 0., without materially altering the microst'ructure typified by Fig. 1.

While the optimum combination of strength and ductility is secured by "extensive plastic deformation in the two-phase field, iabricationproblems frequently render it impossible to roll sheet to the strength level desired in the fabricated lproduct. Bending, =forming, drilling, and like operations, cannot be satisfactorily performed at the desired high strength. It has .been found rthat the alloys processed according to the present invention can be annealed (to the low's'trengthlevel necessary for fabrication, and, 'after fabrication, quenched to the desired high strength, and "still retain "the essentials of the dispersed phase structure. The alpha phase is spheroidized, but remains as discrete bodies rather than continuous masses.

Pig. 2 is a photomicro'graph of an alloy containing 6.8% manganese, balance commercial purity titanium, which, after extensive plastic deformation in the twophase field, had beenheated for 1 hour at 700 C., and water quenched; "it "'w'illbe seen to consist of a beta matrix *cont-a'ining very'numerous relatively small and substanpose of illustration, it has been found as the result of very extensive work that the novel processing is equally applicable to any alloys comprising two ductile phases,

both of which are relatively stable at normal temperatures. Prominent among these are the binary alloys of titanium with molybdenum, chromium, iron and manganese, and the ternary and higher alloys of titanium with th'e metals of this group, and with aluminum up to While in the binary titanium-aluminum alloys the beta iphase is not stable at normal temperatures,

:it is stabilized by 'the addition of one or more beta promoters, such as manganese, molybdenum, chromium and iron, or other beta promoterssuchas vanadium, colum- -bium a'nd tantalum. Other alpha promoters such as tin and/or antimony may be substituted for aluminum on an equivalent basis of about 3% Sn or Sb for 1% Al, the lower effective limit for thesealpha promoters being about 0.5% and the upper limits for tin and antimony 18%, respectively. The weight percentagesof the'ditferent metals of the beta-promoter group, such as manganese, molybdenum, chromium, iron, etc, which whenadded to titanium produce a two-phase structure, vary withtheparticularmetal-the maximum for manganese, for example, :being about 46%, but the atomic percentages fall within the range of about 2 to 15 atomic percent of the beta promoters "present. Below .about'2 atomic percent, the beta phase is either absent altogether Jor present only in a negligible amount; while above about 15 atomic percent the alloys show an all;

7 beta structure on quenching. Typical alloys and their properties as worked in the two-phase field, both with and without subsequent stabilization, are given in the following Table I.

8 vary somewhat with theamount of contaminants present, but in general fall within the following limits: 0.2% offset yield strength 65,00080,000 p. s. i.; ultimate strength 75 ,000-90,000 p. s. i.; tensile elongation 2025%.

TABLE I Tensile properties As Rolled in the Alpha-Beta Field at 650 C. As Stabilized at 600 0.

Composition, Percent (Balance Titanium) Elongation Elongation 0.2% Ultimate in $4" Bend 0.2% Ultimate in 34" Bend Yield Radius Yield Radius 173, 000 12 6. 5 138, 000 149, 000 18 3. 3 175,000 13 6. 5 144,000 160, 000 22 4. 9 184, 000 2 4. 1 132, 000 146, 000 12 2. 9 187, 000 6 6. 2 155, 000 160, 000 12 4. 154, 000 7 4. 6 132, 000 143,000 14 2. 7 160, 000 7. 0 133, 000 142, 000 11 2. 7 146, 000 12 2. 7 000 125, 000 19 1. 7 164,000 8 8. 8 119, 000 141, 000 8 6. 5 159, 000 16 7. 5 122, 000 145, 000 20 6. 2 170, 000 8 6. 1 135, 000 159, 000 5. 8 154, 000 14 4. 8 117, 000 134, 000 21 2. 0 164, 000 8 4. 9 127, 000 139, 000 19 2. 7 175, 000 10 6. 5 138,000 0, 000 20 6. 6 178, 000 4 7. 5 149,000 160, 000 14 4. 4 171, 000 6 7. 3 148, 000 158, 000 13 6. 2 158, 000 10 5. 7 118, 000 138, 000 2. 2 169, 500 11. 7 146, 100 7 158, 400 10 144, 600 23 215, 800 2 183,800 4 9.0Mn-5Cr 3 184, 800 197, 900 3 1 Stabilized at 700 0. 1 Cold worked.

The tensile properties of additional analyses as rolled at 650 C. and thereafter vacuum annealed for one hour at 700 C. are given in the following Table II.

This application'is a continuation-in-part of applications Serial Nos. 132,327, filed December 10, 1949 (now abandoned); 229,143, filed May 31, 1951; 323,155, filed TABLE II Tensile properties as-rolled at 650 C. and annealed 1 hr. at 700 C.

(p. s. i.X1,000)

Mn M0 Cr Fe Other Percent MBR, T

0.2 per- Ultimate Elon. cent yield 1 92 116 5 133 139 16 10 151 157 20 15 156 157 11 2 104 133 16 10 128 146 7 10 126 136 14 15 137 143 23 5 109 127 16 130 12 93 126 19 129 20 117 137 15 122 149 17 169 174 5 0 139 153 18 2. 7 121 147 12 8. 2 163 170 12 8. 9 10. 2 126 136 14 10 5 10 142 150 20 3. 2 10 10 5 133 137 20 0 5 l0 5 117 123 17 0 5 5 10 125 132 23 0 l0 7 7 135 143 24 O 9. 2 5 5 135 135 9 0 10. 5 5 2 134 138 13 0 10. 5 2 5 131 135 11 0 10. 4 5 5 145 149 28 0 The alloys of the invention having tensile elongations as low as about 2% are useful in massive form, for

November 28, 1952 (now abandoned); 385,720, filed October 12, 1953, now abandoned; 424,569, filed April example, forgings, and are useful in the form of rolled 0 21, 1954; 435,754, filed June 10, 1954; 582,574, filed sheet or drawn wire with minimum bend ductilities as high as 20 T.

By way of comparison with the above results, the mechanical properties of the unalloyed titanium base May 3, 1956, now abandoned; and 702,533 filed December 12, 1957.

What is claimed is:

1. A wrought titanium base alloy consisting essentially metal as hot rolled below the beta transus temperature, 75 of about 2 to 15 atomic percent of at least one beta promoting element, characterized by a microstnicture" comprising -'a coherent"adrnixture of'small-bodies of alpha titanium "and =beta-titaniumx 2. -A wrought titanium'base alloy'consi'sting essentially of about: 2 to 15 atomic percent of at least one betapro- .promoting'aelement adapted t stabilize the beta phase at room temperature, .saidalloy having a miciostructure comprising a coherent admixture of a 'jfiii'e dispersion of alph 'a titanium and 'b'eta titanium,'as"produced by plastic deformation in the two-phase'temperature field, and said alloy=-being characterized by high 'tensile strengtl'r 'and good'ductility.

4. A wrought alloy consisting essentially of about 2 to 15 atomic'percentin aggregate ofat leastoneelement selected from thegroup consisting efman aneserqhremium, molybdenum 'and' iron, balance substantially titanium} characterized by a microsti'ucture comprisinga coherent admixture of small-bodies of alpha titanium and beta titanium. e h h 5. A- Wrought alloy consisting"essentially-of abijiit 2 to 15 atomic'percent in aggregate of at leasttwoeleme'nts selected-from the group consisting of manganese,-chr omium, molybdenum and "iron, balance titairliurri, characterized-by amicrostructure-comprising a coherent admixture of smallbodies of alpha titanium and beta titanium, and in having an ultimate strength as hot rolled, of. at least 130,000 p;s. i. and a tensile elongation of at least 2%.

6. A wrought'alloyconsistihg essentially of abo'utZ to 15 atomic percent in aggregate of at least threeelements selected'froni the group consisting-of manganese, chromium, molybdenum and iron, balance titaniunflcharac terized by a microstruc'ture comprising a coherent admixture ofsrnall bodies of alpha titanium and beta titanium, and in havinghigh tensile 'strengthand a tensile elongation of atleast' 2%. I H h 7. A wfought alloy :onsist in'g essentially of about2 to atomic percent in aggregate of at leasttw'o elements selected from the group 'consistingof manganese, chromium, molybdenum and iron, the minimum aggregate manganese and iron content being at least 2 atomic percent, balance titanium, characterized by a microstrueture comprising'a coherent admixture ofsrnall bodies of alpha titanium and betatitaniurn, and in'having a high tensile strength and a tensile elongation of at least 2%.

8. A wrought alloy consisting of about 2 to 15 atomic percent in aggregate of at least two elements selected from the group consisting of manganese, chromium, molybdenum and iron, balance titanium, characterized by a microstructure comprising a coherent admixture of small bodies of alpha titanium and beta titanium and in' having an ultimate strength as hot rolled, of at least 130,000 p. s. i. and a tensile elongation of at least 2%.

9. A wrought titanium base ,alloy containing in percent by weight: about 2 to 16% manganese, up to 0.5% carbon, up to 0.3% oxygen and up to 0.1% nitrogen, balance substantially titanium, said alloy having a microstructure comprising a coherent admixture of small bodies of alpha titanium and beta titanium. l

.10. A wrought titanium base alloy containing in percent by weight about: 2 to 15% chromium, up to 0.5% carbon, up to 0.3% oxygen and up to 0.1% nitrogen, balance substantially titanium, said alloy having a microstructure comprising a coherent admixture of small bodies of alpha titanium and beta titanium. h

11. A Wrought alloy containing in percent by weight about: 2 to 16% iron, up to 0.5% carbon, up to 0.3% oxygen and up to 0.1% nitrogen, balance substantially titanium, said alloy having a microstructure comprising forming the alloy at temperature within the two-phase,

alpha-beta field t6 an extent sufiicient to produce a microstructure characterized by a fine dispersion of the alpha and beta phases, respectively.

14; In the processing of titanium base alloys containtaining about 2'to l5 atomicpercent of at least one beta promoting element and having a mixed alpha-beta microstructure, the method which comprises plastically deforming the alloyat temperature Within the two-phase, alpha-beta field and not higher than 50 C. below the beta .transus temperature, and to an extent suflicient' to :produce a microstructure characterized by a fine dispersion. of the alpha and beta phases, respectively.

.15. In the processing of titanium base alloys containing about 2 to 15 atomic percent of at least one beta promoting element andhaving a mixed alpha-beta microstructure, .the method which comprises plastically deforming tl'l'e alloy attemperature Within the two-phase, alphabeta field and not higher than 50 C. below the beta transus temperature,-and to an extent snfficient to produce a :microstructurecharacterized by a fine dispersion or the alpha and beta phases, respectively, and subsequently aging .the alloy at temperature within the two-phase field such that said fine dispersion of the alpha and beta phases produced by the plastic deformation is not substantially altered; .16, In .the processing of titanium base alloys contain- -ing about 2 ,to l5 atomic percent of at least one beta'promoting element and having a mixed alpha-beta microstructure, the method which comprises plasticall'y neforrning the alloy at temperature within the two-phase, alpha-beta .field and extending from about 400 C. to not more than 50 C. 'below the beta transus temperature, and continuing said plastic deformation until a microstructure is obtained comprising a fine dispersion of the alpha and beta phases, respectively.

.17. In the processing of titanium base alloys containing about 2 to 15 atomic percent of at least one beta promoting element. and having a mixed alpha-beta microstructure, the method which comprises plastically deforming the alloy at temperature within the two-phase, alpha-beta field and extending from about 400 C. to not: morethan 50 C. below the beta transus temperature, and continuingsaid plastic deformation until a microstructure is obtained comprising a fine dispersion of the alpha .and beta phases, respectively, and subsequently aging the alloy at temperature within the two-phase field such :that. the fine dispersion of the alpha and beta phases secured by the plastic deformation is not substantially altered.

18. In the processing of titanium base alloys containing about '2 to 15 atomic percent of at least one elementselected from the group consisting of manganese, chromium, molybdenum and iron, the method wliich comprises plastically deforming the alloy at temperature Within vthe two-phase, alpha-beta field and to an extent suflicient to produce a microstructure characterized by a title dispersion of the alpha and beta phases, respectively. I

19. Inthe processing 'of titanium base alloys containing about 2 to 15 atomic percent of at least one element selected from the group consisting of manganese, chromium, 'r'nolybdenum and iron, the method which 11 comprises plastically deforming the alloy at temperature within the two-phase, alpha-beta field and to an extent sufiicient to produce a microstructure characterized by a fine dispersion of the alpha and beta phases,

respectively, and subsequently aging the alloy at temperature within the two-phase field such that dispersion of the phases produced by the plastic deformation is not substantially altered.

' 20.- In the processing of titanium base alloys containing about 2 to 15 atomic percent of at least one element selected from the group consisting of manganese, chromium, molybdenum and iron, the method which comprises plastically deforming the alloy at temperature within the two-phase, alpha-beta field and extending from about 400 C. to not more than 50 C. below the beta transus temperature, and continuing said plastic deformation until a microstructure is obtained comprising a fine dispersion of the alpha and beta phases, respectively.

21. The method of improving the ratio of ductility to strength in titanium base alloys containing about 2 to 15 atomic percent of at least one beta promoting element and having below the beta transformation temperature, a microstructure containing a mixture of the alpha and beta phases, which comprises: subjecting said alloy to plastic deformation at elevated temperature within the two-phase temperature zone to produce in said alloy a microstructure comprising a fine dispersion of the alpha and beta phases and an enhancement in ductility.

22. The method of improving the ratio of ductility to strength in titanium base alloys containing about 2 to 15 atomic percent of at least one beta promoting element and having below the beta transformation temperature, a microstructure containing a mixture of the alpha and beta phases, which comprises: subjecting said alloy to plastic deformation at elevated temperature within the two-phase temperature zone to produce in said alloy a microstructure comprising a fine dispersion of the alpha and beta phases and an enhancement in ductility; and thereafter subjecting said alloy to a stabilizing heat treatment at elevated temperature within said two-phase temperature zone.

23. The method of improving the ratio of ductility to strength in titanium base alloys containing about 2 to 15 atomic percent of at least one beta promoting element and having below the beta transformation temperature, a microstructure containing a mixture of the alpha and beta phases, which comprises: subjecting said alloy to plastic deformation at elevated temperature within the two-phase temperature zone to produce in said alloy a microstructure comprising a fine dispersion of the alpha and beta phases and an enhancement in ductility; and thereafter quenching said alloy from an elevated temperature Within said two-phase temperature zone.

24. The method of improving the ratio of ductility to strength in titanium base alloys containing about 2 to 15 atomic percent of at least one beta promoting element and having below the beta transformation temperature, a microstructure containing a mixture of the alpha and beta phases, which comprises: subjecting said alloy to plastic deformation at elevated temperature within the two-phase temperature zone to produce in said alloy a microstructure comprising a fine dispersion of the alpha and beta phases and an enhancement in ductility; thereafter quenching said alloy from an elevated temperature within the two-phase temperature zone; and thereafter subjecting said alloy to a stabilizing heat treatment at elevated temperature within said two-phase temperature zone.

25. The method of improving the ratio of ductility to strength in titanium base alloys containing about 2 to 15 atomic percent of at least one beta promoting element and having below the beta transformation temperature, a microstructure containing a mixture of the alpha and beta phases, which comprises: subjecting said alloy-to 12 plastic deformation at a temperature above about 400 C., but below the beta transformation temperature, to produce in said alloy a microstructure comprising a fine dispersion of the alpha and beta phases and an increased ductility. 1

26. The method of improving the ratio of ductility to strength in titanium base alloys containing about 2 to 15 atomic percent of at least one beta promoting element and having below the beta transformation temperature, a microstructure containing a mixture of the alpha and beta phases, which comprises: subjecting said alloy to plastic deformation at a temperature above about 400 C., but below the beta transformation temperature, to produce in said alloy a microstructure comprising a fine dispersion of the alpha and beta phases and an increased ductility; and thereafter subjecting said alloy to a stabilizing heat treatment at a temperature above about 400 C. but below the beta transformation temperature.

27. The method of improving the ratio of ductility to strength in titanium base alloys containing about 2 to 15 atomic percent of at least one beta promoting element and having below the beta transformation temperature, a microstructure containing a mixture of the alpha and beta phases, which comprises: subjecting said alloy to plastic deformation at a temperature above about 400 C., but below the beta transformation temperature to produce in said alloy a microstructure comprising a fine dispersion of the alpha and beta phases and an increased ductility; and thereafter quenching said alloy from a'temperature above about 400 C., but below the beta transformation temperature.

28. The method of improving the ratio of ductility to strength in titanium base alloys containing about 2 to 15 atomic percent of at least one beta promoting element: and having below the beta transformation temperature,. a microstructure containing a mixture of the alpha and. beta phases, which comprises: subjecting said alloy to plastic deformation at a temperature above about 400 C., but below the beta transformation temperature to produce in said alloy a microstructure comprising a fine dispersion of the alpha and beta phases and an increased ductility; thereafter quenching said alloy from a temperature above about 400 C., but below the beta transformation temperature; and thereafter subjecting said alloy to a stabilizing heat treatment at a temperature above about 400 C., but below the beta transformation temperature.

29. A wrought titanium base alloy consisting essentially of: about 2 to 15 atomic percent of at least one beta promoting element, 0.5 to 23% of at least one alpha promoting element selected from the group consisting of aluminum, tin and antimony, but not to exceed about. 18% antimony and about 8% aluminum, characterized by a microstructure comprising a coherent admixture of small bodies of alpha titanium and of beta titanium.

30. A wrought titanium base alloy consisting essentially of: about 2 to 15 atomic percent of a plurality" of beta promoting elements, 0.5 to 23% of at least one: alpha promoting element selected from the group con-- sisting of aluminum, tin and antimony, but not to exceed about 18% antimony and about 8% aluminum, characterized by a microstructure comprising a coherent admixture of small bodies of alpha titanium and of beta titanium.

31. A wrought titanium base alloy consisting essentially of: about 2 to 15 atomic percent of at least one beta promoting element and about 0.5 to 8% of aluminum, characterized by a microstructure comprising a coherent admixture of small bodies of alpha titanium and of beta titanium.

32. A wrought titanium base alloy consisting essentially of: about 2 to 15 atomic percent of a plurality of beta promoting elements and about 0.5 to 8% alu- 13 14' minum, characterized by a microstructure comprising a 2,588,007 Iafiee Mar. 4, 1952 coherent admixture of small bodies of alphatitanium 2,687,350 Craighead Aug. 24, 1954 and of beta tltamum- References Cited in the file of this patent 5 KrOll: Zeitschrift fur Metallkunde, v01. 29 (1937),

UNITED STATES PATENTS Titanium Project: Navy Contract No. NOa (s) 8698 2,206,395 Gelfler July 2, 1940 (Mallory), Report No. 10, Feb. 16, 1948, pages 1, 3-9,

2,287,888 Kroll June 30, 1942 11-14, 

2. A WROUGH TITANIUM BASE ALLOY CONSISTING ESSENTIALLY OF ABOUT: 2 TO 15 ATOMIC PERCENT OF AT LEAST ONE BETA PROMOTING ELEMENT AND 0.5 TO 23% BY WEIGHT OF AT LEAST ONE ALPHA PROMOTING ELEMENT, CHARACTERIZED BY A MICROSTRUCTURE COMPRISING A COHERENT ADMIXTURE OF SMALL BODIES OF ALPHA TITANIUM AND BETA TITANIUM. 